1. Newton’s Second Law of Motion

2. Identify three forces acting on a speeding bullet.
Bell Work
Identify three forces acting on a speeding bullet.
Why do cars sometimes skid going around corners on icy roads?

3. Objectives
Define and apply Newton’s second law of motion to real life situations.
Relate the acceleration of an object to the mass of the object and the force applied to the object.

4. Newton’s Second Law of Motion
This law states that an unbalanced force on an object causes the object to accelerate in the direction of the force.

5. Force of wind
These forces are
unbalanced so the
boat accelerates in
the direction of the
unbalanced force.
20-30 mph
Air/Water Resistance

6. Gravity
Unbalanced
Forces
Table
If gravity becomes greater than the upward force of the table, the papers will accelerate downward.

7. Wagon moves
this way
Unbalanced
Force
Applied

8. Force, Acceleration, and Mass
The greater the force applied to a given object, the greater its acceleration.

9. Force, Acceleration, and Mass
For a given force, the greater the mass of an object, the smaller its acceleration and vice-versa.

10. Newton’s Second Law in Real Life
Why would a truck take longer to accelerate when the driver hits the gas if it were loaded with bricks than if it were empty?
How might you design a car to achieve maximum acceleration?

11. Newton’s Second Law in Real Life
Using Newton’s second law of motion, explain why larger trucks usually need more distance to stop than do smaller trucks.

12. Science, Technology, & Sports
Friction is the main force that slows the speed of athletes in sports such has skiing, swimming, cycling, speed skating, and running. How can these athletes combat the effects of friction?

13. Formula for Newton’s Second Law of Motion
Newton’s second law of motion can be expressed by the formula F = ma.
F stands for force, m stands for mass, and a stands for acceleration.

14. Formula for Newton’s Second Law of Motion
According to this formula, if the force is constant and the mass increases, what will happen to acceleration?

15. Question
Identical twins are riding in identical wagons. A friend gives the first wagon a stronger push than the second. Which twin will experience greater acceleration?

16. Question
Would a car towing a boat take less, the same, or more time to accelerate than it would without the boat? Explain.

17. Question
What will happen to the acceleration of an object if the mass decreases and the force is constant?

18. Question
If two identical objects accelerate at the same rate, what must be true of the force applied to each object?

19. Review
Use Newton’s second law of motion to explain why a free-falling object accelerates.
How is the acceleration of an object affected by the force applied to it?

20. Challenge
Using the formula a = f/m, explain why all objects in free fall have the same acceleration, regardless of mass.